Ceramic dielectrics and methods for forming the same

ABSTRACT

The present invention relates to a ceramic dielectrics. It is difficult to downsize a MgTiO 2  -base ceramic composition conventionally used, having an insufficiently high relative dielectric constant (.di-elect cons. r ), less than 20, while a CaTiO 3  -base ceramic composition, having a small value of Q, is not suitable for electronic devices processing a signal in the high-frequency-bandwidth. Moreover, it is difficult to control the temperature coefficient of resonant frequency of these conventional ceramic compositions. In the present invention, a ceramic dielectrics having a composition represented by xMgTiO 3 .(1-x)CaTiO 3 .y(Ln 1   1-w  Ln 2   w ) 2  Ti 2z  O 3+4z  (wherein Ln 1  and Ln 2  are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w&lt;1, 0.20≦x≦0.80, 0.05≦y≦5.0, and 0.25≦z≦1.5, respectively) contributes to solving the above problems. The ceramic dielectrics according to the present invention can be used as a material for a resonator processing a signal in the microwave-bandwidth, a filter, a capacitor or the like.

FIELD OF THE INVENTION

The present invention relates to a ceramic dielectrics and a method for forming the same.

DESCRIPTION OF THE PRIOR ART

Recently, ceramic dielectrics for high frequency signals have been widely utilized as a material for a resonator used in an antenna duplexer of radio communication equipments such as a mobile phone, a cellular phone and a cordless telephone, a voltage-controlled oscillator (VCO) etc., or a filter used in a tuner for CATV. By using a material having a high dielectric constant for these applications, the wave length of an electromagnetic wave can be shortened to the length of .di-elect cons._(r) ^(-1/2) (.di-elect cons._(r) : relative dielectric constant) under vacuum, so that one wave length, half a wave length or a quarter of a wave length, a resonant condition of an electromagnetic wave, can be shortened. Therefore, when the material is used, electronic devices which process electric signals using a resonance of an electromagnetic wave can be easily downsized.

Characteristics required for the ceramic dielectrics for high frequency signals are:

(1) Since the wave length of an electromagnetic wave is shortened to .di-elect cons._(r) ^(-1/2) in dielectrics, among ceramic dielectrics having the same resonant frequency, those which have a higher dielectric constant can be more downsized. Thus, the dielectric constant should be as high as possible;

(2) The dielectric loss (1/Q) should be small in the high-frequency-bandwidth, that is, the value of Q should be large; and

(3) The variation of a resonant frequency depending on a temperature variation should be small, that is, the dependency on temperature of the relative dielectric constant (.di-elect cons._(r)) should be small.

Besides, a reference clock frequency of electronic devices has been chosen in the microwave-bandwidth in many cases, and at present, the clock frequency of electronic equipment for the consumer is 1 GHz or so. However, as an increase of information content delivered per unit time, and a controlling speed of electronic equipment and a processing speed of signals have become faster, electronic devices for a microwave which can be also used in a higher-frequency-bandwidth (several GHz) are becoming necessary. Accordingly, as a ceramic dielectrics constituting the electronic devices for a microwave, a material having a large value of Q is required to make a microwave loss as small as possible. In addition, a material having a high dielectric constant is required to make the electronic devices as small as possible.

Hitherto, as ceramic dielectrics having the above characteristics, a MgTiO₃ -base and a CaTiO₃ -base ceramic dielectrics have been known.

The conventional MgTiO₃ -base ceramic dielectrics has a large value of Q, but has a relative dielectric constant (.di-elect cons._(r)) of less than 20, which is not sufficiently high. As a result, it is difficult to downsize an element with the MgTiO₃ -base ceramic dielectrics therein. On the other hand, the CaTiO₃ -base ceramic dielectrics has a high dielectric constant, but has a small value of Q. As a result, it is not suitable for electronic devices processing signals in the high-frequency-bandwidth, and it is not suitable for being put to practical use because of its extremely high temperature coefficient of resonant frequency (τ_(f)).

Moreover, since it is difficult to control the temperature coefficient of resonant frequency (τ_(f)) without changing the composition of these materials, it is required to change the temperature coefficient of resonant frequency (τ_(f)) by adding several kinds of additives such as rare earth elements to the above materials. But a ceramic dielectrics available for several requirements cannot be easily provided since the characteristics in changing compositions have not been systematically examined.

DISCLOSURE OF THE INVENTION

The present invention was achieved in order to solve these problems, and it is an object to provide a ceramic dielectrics having a larger value of Q and a higher relative dielectric constant (.di-elect cons._(r)) than ever, whose temperature coefficient of resonant frequency (τ_(f)) can be controlled to an optional value in the range of +100 to -100 ppm/°C., and a method for forming the same.

A ceramic dielectrics (1) according to the present invention have a composition represented by xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln¹ and Ln² are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.).

A ceramic dielectrics (2) according to the present invention substantially comprise a composition as a principal component represented by xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln¹ and Ln² are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0<a≦0.2) to 1 mol of the principal component.

A ceramic dielectrics (3) according to the present invention have a composition represented by xMgTiO₃.(1-x)CaTiO₃.y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln² is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.).

A ceramic dielectrics (4) according to the present invention substantially comprise a composition as a principal component represented by xMgTiO₃.(1-x)CaTiO₃.y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln² is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives, in the range of a mol (where, 0<a≦0.2) to 1 mol of the principal component.

The above ceramic dielectrics (1)-(4) have a high relative dielectric constant (.di-elect cons._(r)), 30-70, and a small dielectric loss because of a high value of Q, 3000 or more at a measuring frequency of 3 GHz, and by changing their compositions and so on, their temperature coefficient of resonant frequency (τ_(f)) can be controlled to a particular value in the range of +100 to -100 ppm/°C.

Besides, by making use of the electric characteristics of these ceramic dielectrics (1)-(4), a resonator for high frequency signals, a filter etc. can be sharply downsized.

A method for forming a ceramic dielectrics (1) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln¹, and Ln² (here, Ln¹ and Ln² are lanthanoids) in such a proportion as a ceramic composition represented by xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln¹ and Ln² are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) is formed after being sintered, mixing, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere.

A method for forming a ceramic dielectrics (2) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln¹, and Ln² (here, Ln¹ and Ln² are lanthanoids) and a powder as sintering agents selected from compounds containing Zn and/or Mn in such a proportion as a ceramic composition substantially comprising a composition as a principal component represented by xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln¹ and Ln² are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0<a≦0.2) to 1 mol of the principal component is formed after being sintered, mixing, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere.

A method for forming a ceramic dielectrics (3) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln¹, and Ln² (here, Ln¹ and Ln² are lanthanoids) in such a proportion as a ceramic composition represented by xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln¹ and Ln² are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere.

A method for forming a ceramic dielectrics (4) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln¹, and Ln² (here, Ln¹ and Ln² are lanthanoids) and a powder as sintering agents selected from compounds containing Zn and/or Mn in such a proportion as a ceramic composition substantially comprising a composition as a principal component represented by xMgTiO₃.(1-x)CaTiO₃. y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln¹ and Ln² are lanthanoids, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0<a≦0.2) to 1 mol of the principal component is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere.

A method for forming ceramic dielectrics (5) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Nd, and Ln² (here, Ln² is a lanthanoid) in such a proportion as a ceramic composition represented by xMgTiO₃.(1-x)CaTiO₃. y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln² is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere.

A method for forming a ceramic dielectrics (6) according to the present invention comprises the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Nd, and Ln² (here, Ln² is a lanthanoid) and a powder as sintering agents selected from compounds containing Zn and/or Mn in such a proportion as a ceramic composition substantially comprising a composition as a principal component represented by xMgTiO₃.(1-x)CaTiO₃. y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) (wherein Ln² is a lanthanoid, and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0 and 0.25≦z≦1.5, respectively.) and ZnO and/or MnO as additives in the range of a mol (where, 0<a≦0.2) to 1 mol of the principal component is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere.

According to the above methods for forming a ceramic dielectrics (1)-(6), a sintered body can have a uniform grain size and a ceramic dielectrics having a high relative dielectric constant (.di-elect cons._(r)), 30-70, and a small dielectric loss because of a high value of Q, 3000 or more at a measuring frequency of 3 GHz, whose temperature coefficient of resonant frequency (τ_(f)) can be controlled to a particular value in the range of +100 to -100 ppm/°C. by changing their compositions etc., can be easily manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a diagrammatic plain figure showing an apparatus used for measuring electric characteristics of the ceramic dielectrics according to Examples in the present invention, and FIG. 1(b) is a front view thereof.

FORM FOR CONDUCTING THE INVENTION

In the above methods for forming a ceramic dielectrics, raw materials are selected from compounds each of which contains one or two of Mg, Ca, Ti, and lanthanoids, and are prepared. In the case where addition of sintering agents is required, a powder selected from compounds containing Zn and Mn is added to the prepared raw materials. The compounds constituting these raw materials are not limited to oxides of the above elements and other compounds are available. For example, raw materials of carbonate, oxalate, nitrate, and alkoxide, which give oxides after being sintered, are exemplified. When oxides or carbonates of the above elements are used as raw materials, the average grain size of these compounds is preferably several μm or so. These raw materials are wet mixed in the usual way, and then dried, calcined, crushed, granulated, pressed and so on, so as to form a pressed body having a prescribed shape. After sintering the same, a ceramic is obtained.

To be concrete, every raw material is accurately weighed in the above composition, which is wet mixed with balls, a well-known dispersant and distilled water in a pot mill for 24 hours or so, and finally a raw material mixture in a slurry is obtained. Next, the mixture in a slurry is dried and crushed. Then, the crushed powder may be transferred to a zirconia crucible for sintering, be calcined and synthesized at a temperature of 1000°-1200° C., and be crushed again, depending on necessity. As for the temperature condition of calcination and synthesis, the above range of temperature is preferable, since at a temperature of less than 1000° C., a large amount of raw material is left and uniform sintering is prohibited, while at a temperature of over 1200° C., sintering starts, which makes pulverizing difficult, and in both cases the value of Q tends to decrease.

Then, the crushed powder is granulated to a powder having an almost uniform grain size. After an organic binder etc. is added to the granulated powder, a pressed body having a prescribed shape is formed. As another way, a granulation treatment may be conducted by a spray drier etc. on the crushed powder with an organic binder etc. added thereto and a pressed body may be formed from the obtained powder.

Then, the ceramic dielectric is obtained by defatting the obtained pressed body at a temperature of 600° C. or so, placing the defatted pressed body on a plate for sintering made of MgO etc., and sintering the pressed body placed thereon at a temperature of 1200°-1600° C. in the air or an oxygen atmosphere for 2-8 hours. When the sintering temperature is less than 1200° C., the pressed body is not sufficiently made fine, its value of Q becomes small, and its relative dielectric constant (.di-elect cons._(r)) does not become high, while when the sintering temperature is over 1600° C., the ceramic dielectric itself becomes soft and the shape of the pressed body before being sintered cannot be kept. As a result, the above range of temperature is preferable.

The ceramic dielectrics formed by the above method have a high relative dielectric constant (.di-elect cons._(r)), 30-70, and a large value of Q, 3000 or more at a measuring frequency of 3 GHz. In addition, it is possible to control its temperature coefficient of resonant frequency (τ_(f)) to a particular value in the range of +100 to -100 ppm/°C. by changing x, y etc. in the composition formula. And the tissue structure of the ceramic dielectrics has an almost uniform grain size and is extremely fine, having a sintering density of 96.0-100% or so to the theoretical density, and is excellent in mechanical characteristics, so that it is suitable for use for a resonator or the like.

In the ceramic dielectrics, Ln¹ and Ln² are rare earth lanthanoid elements, and as the elements, La, Ce, Nd, Gd, Sm, and Dy are exemplified. As mentioned before, the temperature coefficient of resonant frequency (τ_(f)) can be controlled by changing the mixing ratio of these lanthanoids (y).

X is an atom ratio of Mg to a total amount of Mg and Ca in the ceramic dielectrics. When x is less than 0.20, Q becomes small, 3000 or less (at 3 GHz), and the temperature coefficient of resonant frequency (τ_(f)) becomes larger than 100, while when x is over 0.80, the relative dielectric constant (.di-elect cons._(r)) becomes small, less than 30.

Y is a mol ratio of (Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) to (xMgTiO₃ +(1-x)CaTiO₃). When y is less than 0.05, the temperature coefficient of resonant frequency (τ_(f)) becomes too large, while when y is over 5.0, Q becomes small, 3000 or less.

Z is a mol ratio of Ti to lanthanoids. When z is less than 0.25, Q becomes small, 3000 or less, while when z is over 1.5, the temperature coefficient of resonant frequency (τ_(f)) becomes too large.

A is mols of sintering agents to 1 mol of the principal component. The sintering agents contribute to a rise in Q when it is added in the case where sintering is difficult because of a small amount of Ti. On the other hand, the temperature coefficient of resonant frequency (τ_(f)) becomes small by adding the sintering agents. When a is over 0.20, Q becomes small, 3000 or less.

DESCRIPTION OF PREFERRED EMBODIMENTS

Examples and Comparative Examples of a ceramic dielectric and a method for forming the same according to the present invention are described below.

First, a method for forming ceramic dielectrics according to Examples is explained.

Raw materials selected from MgO, CaCo₃, TiO₂, Ln¹ ₂ O₃, and Ln² ₂ O₃ (Ln¹ and Ln² are lanthanoids), having an average grain size of some μm, were prepared in the proportions shown in Tables 1-5. Here, w, x, y, 2z, and a in Tables 1-5 correspond to the letters representing the ceramic dielectrics (1) and (2). In addition, as sintering agents, ZnO and MnCO₃ having the same average grain size as them were used.

A method for forming a sintered body is as described in the "FORM FOR CONDUCTING THE INVENTION", and as a raw material for pressing, powder calcined at 1000° C., and then crushed and granulated by addition of an organic binder etc. were used.

As for the composition of the ceramic dielectrics obtained by the above sintering, by conducting an ICP emission spectrochemical analysis after the ceramic dielectric was dissolved in an acid, it was confirmed that the composition of the sintered body is the same as the preparation composition of the raw materials. For further observation of the structure of the sintered body, an etching treatment was conducted on the sintered body after being broken, and the surface thereof was observed with a scanning electron microscope (SEM). As a result, it was proved that the ceramic dielectrics according to Examples have a fine structure formed from particles having an almost uniform grain size.

And in order for measuring electric characteristics, a sample for the measurement of electric characteristics was formed by sufficiently washing the obtained sintered body in distilled water, and then polishing it into such a shape as it has parallel main surfaces and a resonant frequency of 3 GHz.

Next, a method for measuring electric characteristics of the ceramic dielectrics according to Examples is explained.

As the electric characteristics, the resonant frequency, relative dielectric constant (.di-elect cons._(r)) and Q were measured by the Hakki-Coleman dielectric resonator method.

FIG. 1(a) is a plain figure diagrammatically showing an apparatus used for measuring the electric characteristics, and FIG. 1(b) is a front view thereof.

A sample (ceramic dielectric) 11, a subject of the measurement, is fixed in the state of being interposed between two parallel metal plates 12. 13 represents a column for keeping the metal plate stable on the sample.

In measuring the dielectric constant, the frequency characteristic was measured by oscillating a high frequency from a probe 14 of a network analyzer, and the relative dielectric constant (.di-elect cons._(r)) was calculated from the obtained resonant frequency peak in TEO1 δ mode and the dimensions of a sample 11. As for measuring Q, the surface specific resistance of a metal plate 12 was found by using a standard sample, from which the dielectric loss for a metal plate 12 was found, and Q of a sample 11 was calculated by subtracting the dielectric loss for a metal plate 12 from the total dielectric loss. And the temperature coefficient of resonant frequency (τ_(f)) was measured in the atmospheric temperature range from -30° to +85° C.

As the samples for the measurement, fifty samples of every Example (composition) were manufactured and the electric characteristics of each sample 11 were measured, and average values thereof were calculated. The results are shown in Tables 1-5.

Here, as Comparative Examples, the electric characteristics of the ceramic dielectrics having a composition outside the range of the present invention, manufactured under the same conditions as Examples, and those of the ceramic dielectrics having a composition within the range of the present invention, manufactured at a sintering temperature of less than 1200° C. or more than 1600° C., were measured. The results are also shown in Tables 1-5. Comparative Examples are marked *.

                                      TABLE 1                                      __________________________________________________________________________                                   Relative   Tempera-                                                       Sintering                                                                           Dielec-    ture                                  Composition of Ceramic Dielectrics                                                                      Tempera-                                                                            tric       Coeffi-                               Sample Ln.sup.1  Sintering                                                                              ture Constant                                                                            Value of Q                                                                           cient τ.sup.f                     No. x  (w = 0)                                                                            y  2z Agent                                                                               a  (°C.)                                                                        (ε.sub.r)                                                                   (at 3 GHz)                                                                           (ppm/°C.)                                                                     Note                            __________________________________________________________________________     1   0.900                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 20   50000 -15   *                               2   0.800                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 32   11000 9                                     3   0.700                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 42   8000  18                                    4   0.600                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 56   7300  31                                    5   0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 62   6500  48                                    6   0.400                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 67   6200  56                                    7   0.300                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 69   6000  71                                    8   0.200                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 70   4700  85                                    9   0.100                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1400 71   1800  101   *                               10  0.500                                                                             Nd  0.000                                                                             1.000   0.000                                                                             1400 72   1500  125   *                               11  0.500                                                                             Nd  0.005                                                                             1.000   0.000                                                                             1400 69   3200  117   *                               12  0.500                                                                             Nd  0.040                                                                             1.000   0.000                                                                             1400 68   1100  111   *                               13  0.500                                                                             Nd  0.050                                                                             1.000   0.000                                                                             1400 67   3800  63                                    14  0.500                                                                             Nd  0.250                                                                             1.000   0.000                                                                             1400 58   6300  40                                    15  0.500                                                                             Nd  0.500                                                                             1.000   0.000                                                                             1400 52   6000  37                                    16  0.500                                                                             Nd  1.000                                                                             1.000   0.000                                                                             1400 49   6700  19                                    17  0.500                                                                             Nd  1.500                                                                             1.000   0.000                                                                             1400 46   6600  6                                     18  0.500                                                                             Nd  2.500                                                                             1.000   0.000                                                                             1400 39   3500  -10                                   19  0.500                                                                             Nd  5.000                                                                             1.000   0.000                                                                             1400 45   6000  -15                                   20  0.500                                                                             Nd  5.300                                                                             1.000   0.000                                                                             1400 35   1000  --    *                               21  0.500                                                                             Sm  0.005                                                                             1.000   0.000                                                                             1400 63   5700  109   *                               22  0.500                                                                             Sm  0.040                                                                             1.000   0.000                                                                             1400 56   2300  105   *                               23  0.500                                                                             Sm  0.050                                                                             1.000   0.000                                                                             1400 58   5200  62                                    24  0.500                                                                             Sm  0.500                                                                             1.000   0.000                                                                             1400 50   5900  38                                    25  0.500                                                                             Sm  1.000                                                                             1.000   0.000                                                                             1400 47   6200  18                                    26  0.500                                                                             Sm  1.500                                                                             1.000   0.000                                                                             1400 42   5900  -15                                   27  0.500                                                                             Sm  2.500                                                                             1.000   0.000                                                                             1400 31   3800  -24                                   28  0.500                                                                             Sm  5.000                                                                             1.000   0.000                                                                             1400 30   3500  -15                                   29  0.500                                                                             Sm  5.300                                                                             1.000   0.000                                                                             1400 24   1500  --    *                               __________________________________________________________________________

                                      TABLE 2                                      __________________________________________________________________________                                   Relative   Tempera-                                                       Sintering                                                                           Dielec-    ture                                  Composition of Ceramic Dielectrics                                                                      Tempera-                                                                            tric       Coeffi-                               Sample Ln.sup.1  Sintering                                                                              ture Constant                                                                            Value of Q                                                                           cient τ.sup.f                     No. x  (w = 0)                                                                            y  2z Agent                                                                               a  (°C.)                                                                        (ε.sub.r)                                                                   (at 3 GHz)                                                                           (ppm/°C.)                                                                     Note                            __________________________________________________________________________     30  0.500                                                                             Gd  0.005                                                                             1.000   0.000                                                                             1400 61   1800  105   *                               31  0.500                                                                             Gd  0.040                                                                             1.000   0.000                                                                             1400 60   1500  135   *                               32  0.500                                                                             Gd  0.050                                                                             1.000   0.000                                                                             1400 56   4300  60                                    33  0.500                                                                             Gd  0.500                                                                             1.000   0.000                                                                             1400 49   4900  37                                    34  0.500                                                                             Gd  1.000                                                                             1.000   0.000                                                                             1400 45   5700  10                                    35  0.500                                                                             Gd  1.500                                                                             1.000   0.000                                                                             1400 41   7200  21                                    36  0.500                                                                             Gd  2.500                                                                             1.000   0.000                                                                             1400 31   3200  35                                    37  0.500                                                                             Gd  5.000                                                                             1.000   0.000                                                                             1400 30   3700  -35                                   38  0.500                                                                             Gd  5.300                                                                             1.000   0.000                                                                             1400 20   1300  40    *                               39  0.500                                                                             Dy  0.005                                                                             1.000   0.000                                                                             1400 60   1300  104   *                               40  0.500                                                                             Dy  0.040                                                                             1.000   0.000                                                                             1400 57    500  120   *                               41  0.500                                                                             Dy  0.050                                                                             1.000   0.000                                                                             1400 55   4900  58                                    42  0.500                                                                             Dy  0.500                                                                             1.000   0.000                                                                             1400 48   5500  36                                    43  0.500                                                                             Dy  1.000                                                                             1.000   0.000                                                                             1400 44   6200  10                                    44  0.500                                                                             Dy  1.500                                                                             1.000   0.000                                                                             1400 40   6100  -23                                   45  0.500                                                                             Dy  2.500                                                                             1.000   0.000                                                                             1400 34   3200  -61                                   46  0.500                                                                             Dy  5.000                                                                             1.000   0.000                                                                             1400 30   3200  -47                                   47  0.500                                                                             Dy  5.300                                                                             1.000   0.000                                                                             1400 27   1800  --    *                               48  0.500                                                                             Ce  0.005                                                                             1.000   0.000                                                                             1400 70   1300  121   *                               49  0.500                                                                             Ce  0.050                                                                             1.000   0.000                                                                             1400 68   3900  65                                    50  0.500                                                                             Ce  0.500                                                                             1.000   0.000                                                                             1400 59   4300  42                                    51  0.500                                                                             Ce  1.000                                                                             1.000   0.000                                                                             1400 53   5100  21                                    52  0.500                                                                             Ce  1.500                                                                             1.000   0.000                                                                             1400 45   4200  4                                     53  0.500                                                                             Ce  2.500                                                                             1.000   0.000                                                                             1400 33   4000  -15                                   54  0.500                                                                             Nd  0.150                                                                             1.000                                                                             MnO  0.010                                                                             1400 51   6600  49                                    55  0.500                                                                             Nd  0.150                                                                             1.000                                                                             MnO  0.100                                                                             1400 50   6500  47                                    56  0.500                                                                             Nd  0.150                                                                             1.000                                                                             MnO  0.180                                                                             1400 55   6800  40                                    57  0.500                                                                             Nd  0.150                                                                             1.000                                                                             MnO  0.210                                                                             1400 --   --    --    *                               58  0.500                                                                             Nd  0.150                                                                             1.000                                                                             ZnO  0.010                                                                             1400 60   6900  47                                    59  0.500                                                                             Nd  0.150                                                                             1.000                                                                             ZnO  0.100                                                                             1400 58   7000  45                                    60  0.500                                                                             Nd  0.150                                                                             1.000                                                                             ZnO  0.180                                                                             1400 53   7200  39                                    61  0.500                                                                             Nd  0.150                                                                             1.000                                                                             ZnO  0.210                                                                             1400 --    800  --    *                               __________________________________________________________________________

                                      TABLE 3                                      __________________________________________________________________________                                   Relative   Tempera-                                                       Sintering                                                                           Dielec-    ture                                  Composition of Ceramic Dielectrics                                                                      Tempera-                                                                            tric       Coeffi-                               Sample Ln.sup.1  Sintering                                                                              ture Constant                                                                            Value of Q                                                                           cient τ.sup.f                     No. x  (w = 0)                                                                            y  2z Agent                                                                               a  (°C.)                                                                        (ε.sub.r)                                                                   (at 3 GHz)                                                                           (ppm/°C.)                                                                     Note                            __________________________________________________________________________     62  0.500                                                                             Nd  0.150                                                                             0.400   0.000                                                                             1400 28   1600  35    *                               63  0.500                                                                             Nd  0.150                                                                             0.500   0.000                                                                             1400 60   6400  21                                    64  0.500                                                                             Nd  0.150                                                                             0.750   0.000                                                                             1400 61   6700  50                                    65  0.500                                                                             Nd  0.150                                                                             1.250   0.000                                                                             1400 64   6500  40                                    66  0.500                                                                             Nd  0.150                                                                             1.500   0.000                                                                             1400 62   5200  39                                    67  0.500                                                                             Nd  0.150                                                                             2.000   0.000                                                                             1400 63   5400  37                                    68  0.500                                                                             Nd  0.150                                                                             3.100   0.000                                                                             1400 76   4600  135   *                               69  0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1100 23    800  --    *                               70  0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1150 27    900  --    *                               71  0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1200 60   6000  41                                    72  0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1300 61   5700  47                                    73  0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1500 62   6200  48                                    74  0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1600 63   5600  49                                    75  0.500                                                                             Nd  0.150                                                                             1.000   0.000                                                                             1650 unmeasured owing to                                                                             *                                                             dissolution                                      76  0.500                                                                             Nd  0.150                                                                             1.000                                                                             MnO  0.100                                                                             1150 29   1100  47    *                               77  0.500                                                                             Nd  0.150                                                                             1.000                                                                             MnO  0.100                                                                             1200 60   6500  41                                    78  0.500                                                                             Nd  0.150                                                                             1.000                                                                             MnO  0.100                                                                             1300 60   6000  41                                    79  0.500                                                                             Nd  0.150                                                                             1.000                                                                             ZnO  0.100                                                                             1150 27    900  44    *                               80  0.500                                                                             Nd  0.150                                                                             1.000                                                                             ZnO  0.100                                                                             1200 59   6800  46                                    81  0.500                                                                             Nd  0.150                                                                             1.000                                                                             ZnO  0.100                                                                             1300 60   7100  47                                    82  0.500                                                                             La  0.150                                                                             1.000   0.000                                                                             1400 70   4900  93                                    83  0.500                                                                             La  0  1.000   0.000                                                                             1400 57   3400  800   *                               84  0.500                                                                             La  0.001                                                                             1.000   0.000                                                                             1400 61   3900  148   *                               85  0.500                                                                             La  0.010                                                                             1.000   0.000                                                                             1400 52   4200  125   *                               86  0.500                                                                             La  0.100                                                                             1.000   0.000                                                                             1400 49   4300  69                                    87  0.500                                                                             La  1.000                                                                             1.000   0.000                                                                             1400 51   4700  63                                    88  0.500                                                                             La  3.000                                                                             1.000   0.000                                                                             1400 47   3500  21                                    89  0.500                                                                             La  4.900                                                                             1.000   0.000                                                                             1400 43   3400  11                                    90  0.500                                                                             La  5.500                                                                             1.000   0.000                                                                             1400 41    360  -100  *                               91  0.700                                                                             La  0.500                                                                             1.000   0.000                                                                             1400 64   6300  93                                    92  0.700                                                                             La  2.500                                                                             1.000   0.000                                                                             1400 59   3800  19                                    93  0.700                                                                             La  6.000                                                                             1.000   0.000                                                                             1400 43    560  0     *                               94  1.000                                                                             La  3.000                                                                             1.000   0.000                                                                             1400 85    490  490   *                               95  1.000                                                                             La  6.000                                                                             1.000   0.000                                                                             1400 47    300  580   *                               __________________________________________________________________________

                                      TABLE 4                                      __________________________________________________________________________                                     Relative   Tempera-                                                       Sintering                                                                           Dielec-    ture                                Composition of Ceramic Dielectrics                                                                        Tempera-                                                                            tric       Coeffi-                             Sample Ln.sup.1    Sintering                                                                              ture Constant                                                                            Value of Q                                                                           cient τ.sup.f                   No. x  Ln.sup.2                                                                          w  y  2z Agents                                                                              a  (°C.)                                                                        (ε.sub.r)                                                                   (at 3 GHz)                                                                           (ppm/°C.)                                                                    Note                           __________________________________________________________________________     96  0.500                                                                             Nd 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 63   4800  62                                         Sm                                                                      97  0.500                                                                             Nd 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 60   4100  61                                         Gd                                                                      98  0.500                                                                             Nd 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 60   4200  60                                         Dy                                                                      99  0.500                                                                             Nd 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 67   3600  64                                         Ce                                                                      100 0.500                                                                             Sm 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 58   4900  61                                         Gd                                                                      101 0.500                                                                             Sm 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 60   4200  60                                         Dy                                                                      102 0.500                                                                             Sm 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 57   4200  63                                         Ce                                                                      103 0.500                                                                             Sm 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 51   4500  59                                         Dy                                                                      104 0.500                                                                             Gd 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 60   4000  63                                         Ce                                                                      105 0.500                                                                             Dy 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 61   4200  51                                         Ce                                                                      106 0.500                                                                             Nd 0.010                                                                             0.500                                                                             1.000   0.000                                                                             1400 52   10000 25                                         La                                                                      107 0.500                                                                             Nd 0.100                                                                             0.500                                                                             1.000   0.000                                                                             1400 56   11500 25                                         La                                                                      108 0.500                                                                             Nd 0.200                                                                             0.500                                                                             1.000   0.000                                                                             1400 59   12100 37                                         La                                                                      109 0.500                                                                             Nd 0.300                                                                             0.500                                                                             1.000   0.000                                                                             1400 61   11300 44                                         La                                                                      110 0.500                                                                             Nd 0.400                                                                             0.500                                                                             1.000   0.000                                                                             1400 64   10800 56                                         La                                                                      111 0.500                                                                             Nd 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 66   9700  63                                         La                                                                      __________________________________________________________________________

                                      TABLE 5                                      __________________________________________________________________________                                     Relative   Tempera-                                                       Sintering                                                                           Dielec-    ture                                Composition of Ceramic Dielectrics                                                                        Tempera-                                                                            tric       Coeffi-                             Sample Ln.sup.1    Sintering                                                                              ture Constant                                                                            Value of Q                                                                           cient τ.sup.f                   No. x  Ln.sup.2                                                                          w  y  2z Agents                                                                              a  (°C.)                                                                        (ε.sub.r)                                                                   (at 3 GHz)                                                                           (ppm/°C.)                                                                    Note                           __________________________________________________________________________     112 0.500                                                                             Nd 0.600                                                                             0.500                                                                             1.000   0.000                                                                             1400 66   8300  65                                         La                                                                      113 0.500                                                                             Nd 0.700                                                                             0.500                                                                             1.000   0.000                                                                             1400 68   5200  73                                         La                                                                      114 0.500                                                                             Nd 0.800                                                                             0.500                                                                             1.000   0.000                                                                             1400 69   5000  77                                         La                                                                      115 0.500                                                                             Nd 0.900                                                                             0.500                                                                             1.000   0.000                                                                             1400 70   4800  91                                         La                                                                      116 0.500                                                                             Nd 0.500                                                                             0  1.000   0.000                                                                             1400 56   3500  780  *                                     La                                                                      117 0.500                                                                             Nd 0.500                                                                             0.001                                                                             1.000   0.000                                                                             1400 57   4100  190  *                                     La                                                                      118 0.500                                                                             Nd 0.500                                                                             0.010                                                                             1.000   0.000                                                                             1400 55   5100  160  *                                     La                                                                      119 0.500                                                                             Nd 0.500                                                                             0.100                                                                             1.000   0.000                                                                             1400 54   4100  71                                         La                                                                      120 0.500                                                                             Nd 0.500                                                                             1.000                                                                             1.000   0.000                                                                             1400 49   4300  53                                         La                                                                      121 0.500                                                                             Nd 0.500                                                                             3.000                                                                             1.000   0.000                                                                             1400 46   3900  18                                         La                                                                      122 0.500                                                                             Nd 0.500                                                                             4.500                                                                             1.000   0.000                                                                             1400 43   3300  -3                                         La                                                                      123 0.500                                                                             Nd 0.500                                                                             5.500                                                                             1.000   0.000                                                                             1400 35   870   -105 *                                     La                                                                      124 0.700                                                                             Nd 0.500                                                                             0.500                                                                             1.000   0.000                                                                             1400 65   6900  78                                         La                                                                      125 0.700                                                                             Nd 0.500                                                                             4.500                                                                             1.000   0.000                                                                             1400 46   3300  11                                         La                                                                      126 0.700                                                                             Nd 0.500                                                                             6.000                                                                             1.000   0.000                                                                             1400 44   950   8    *                                     La                                                                      __________________________________________________________________________

As obvious from the results in Tables 1-5, the ceramic dielectrics according to Examples have a high relative dielectric constant (.di-elect cons._(r)), 30-70, and a small dielectric loss because of a large value of Q, 3000 or more at a measuring frequency of 3 GHz, and the temperature coefficient of resonant frequency (τ_(f)) can be controlled to be a particular value within the range of +100° to -100 ppm/°C. by changing the ratio (x) of MgO to CaO, or the ratio (y) of (xMgTiO₃.(1-x)CaTiO₃) to (Ln¹ ₁ -w Ln² _(w))₂ Ti_(2z) O_(3+4z). And by setting the sintering temperature at a temperature of 1200°-1600° C., a ceramic dielectrics having the above excellent electric characteristics can be manufactured.

On the other hand, among the ceramic dielectrics according to Comparative Examples, those having x of less than 0.20 or more than 0.80, y of less than 0.05 or more than 5.0, z of less than 0.25 or more than 1.5, and a of more than 0.2, had at least one of Q, relative dielectric constant (.di-elect cons._(r)) and temperature coefficient of resonant frequency (τ_(f)) outside the above ranges. As a result, it is difficult to use them as a material for a resonator, a filter or the like.

And as for the ceramic dielectrics formed at a sintering temperature of less than 1200° C. or more than 1600° C., the obtained electric characteristics thereof were not desirable, either.

POSSIBILITY OF INDUSTRIAL APPLICATION

Ceramic dielectrics according to the present invention can be used as a material for a high-performance resonator processing a signal in the microwave-bandwidth, a filter, a capacitor or the like. 

I claim:
 1. A ceramic dielectric consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln¹ and Ln² are lanthanoids and w, x, y, and z are values in the range of 0≦w<1, 0.20≦x≦0.80, 0.1≦y≦5.0, and 0.25≦z≦1.5, respectively.
 2. A ceramic dielectric consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln¹ and Ln² are lanthanoids and w, x, y, and z are values in the range of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0, and 0.25≦z≦1.5, respectively and ZnO and/or MnO as additives in the range of a to 1 mol of the principal component, where the value of a is 0<a≦0.2.
 3. A ceramic dielectric consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln² is a lanthanoid and w, x, y, and z are values in the range of 0≦w<1, 0.20≦x≦0.80, 0.1≦y≦5.0, and 0.25≦z≦1.5, respectively.
 4. A ceramic dielectric consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln² is a lanthanoid and w, x, y, and z are values in the range of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0, and 0.25≦z≦1.5, respectively and ZnO and/or MnO as additives in the range of a to 1 mol of the principal component, where the value of a is 0<a≦0.2.
 5. A method for forming ceramic dielectrics, comprising the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln¹, and Ln², wherein Ln¹ and Ln² are lanthanoids in such ceramic dielectrics after being sintered consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln¹ and Ln² are lanthanoids and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.01≦y≦5.0, and 0.25≦z≦1.5, respectively, mixing, pressing, and then sintering the same at a temperature of 1200°-1600° C. in air or an oxygen atmosphere.
 6. A method for forming ceramic dielectrics, comprising the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln¹, and Ln², wherein Ln¹ and Ln² are lanthanoids, and a powder as sintering agents selected from compounds containing Zn and/or Mn in such ceramic dielectrics after being sintered consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln¹ and Ln² are lanthanoids and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0, and 0.25≦z≦1.5, respectively, and ZnO and/or MnO as additives in the range of a to 1 mol of the principal component, where the value of a is 0<a≦0.2, mixing, pressing, and then sintering the same at a temperature of 1200°-1600° C. in air or an oxygen atmosphere.
 7. A method for forming ceramic dielectrics, comprising the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Ln¹, and Ln², wherein Ln¹ and Ln² are lanthanoids, and a powder as sintering agents selected from compounds containing Zn and/or Mn in such ceramic dielectrics after being sintered consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln¹ and Ln² are lanthanoids and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.1≦y≦5.0, and 0.25≦z≦1.5, respectively, and ZnO and/or MnO as additives in the range of a to 1 mol of the principal component, where the value of a is 021 a≦0.2, is formed after being sintered, mixing, pressing, and then sintering the same at a temperature of 1200°-1600° C. in air or an oxygen atmosphere.
 8. A method for forming ceramic dielectrics, comprising the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti Ln¹, and Ln², wherein Ln¹ and Ln² are lanthanoids, and a powder as sintering agents selected from compounds containing Zn and/or Mn in such ceramic dielectrics after being sintered consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Ln¹ _(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z) , wherein Ln¹ and Ln² are lanthanoids and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0, and 0.25≦z≦1.5, respectively, and ZnO and/or MnO as additives in the range of a to 1 mol of the principal component, where the value of a is 0<a≦0.2, is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in air or an oxygen atmosphere.
 9. A method for forming ceramic dielectrics, comprising the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Nd, and Ln², wherein Ln² is a lanthanoid, and a powder as sintering agents selected from compounds containing Zn and/or Mn in such ceramic dielectrics after being sintered consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln² is a lanthanoid and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.1≦y≦5.0, and 0.25≦z≦1.5, respectively, and ZnO and/or MnO as additives in the range of a to 1 mol of the principal component, where the value of a is 0<a≦0.2, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in air or an oxygen atmosphere.
 10. A method for forming ceramic dielectrics, comprising the steps of preparing raw materials selected from compounds each of which contains one of Mg, Ca, Ti, Nd, and Ln², wherein Ln² is a lanthanoid, and a powder as sintering agents selected from compounds containing Zn and/or Mn in such ceramic dielectrics after being sintered consisting essentially of xMgTiO₃.(1-x)CaTiO₃.y(Nd_(1-w) Ln² _(w))₂ Ti_(2z) O_(3+4z), wherein Ln² is a lanthanoid and w, x, y, and z are values in the ranges of 0≦w<1, 0.20≦x≦0.80, 0.05≦y≦5.0, and 0.25≦z≦1.5, respectively, and ZnO and/or MnO as additives in the range of a to 1 mol of the principal component, where the value of a is 0<a≦0.2, is formed after being sintered, mixing, calcining, granulating, pressing, and then sintering the same at a temperature of 1200°-1600° C. in air or an oxygen atmosphere. 